(1) Field of the Invention
The present invention relates to a setting type resin composition excellent in the heat resistance and mechanical properties. More particularly, the present invention relates to a setting type resin composition having highly improved heat resistance and mechanical properties, which comprises a setting type resin and a substantially linear, high-molecular-weight novolak type substituted phenolic resin, optionally together with an inorganic filler.
(2) Description of the Prior Art
Setting type resins such as epoxy resins, urethane resins, urea resins, melamine resins and phenolic resins are ordinarily used in the form of setting type resin compositions formed by adding curing agents and, if necessary, inorganic fillers to these setting resins, and these resin compositions are used for manufacture of various molded articles through molding and curing. Although cured products of these setting type resin compositions are excellent in the mechanical properties at relatively low temperatures approximating to normal temperatures, they are inferior in the heat resistance and mechanical characteristics at high temperatures such as thermal distortion temperatures, the thermal distortion resistance, flexural strength, mechanical strength and dimension stability. Therefore, these setting type resin compositions cannot be utilized for manufacture of molded articles to be used under heating conditions.
As means for improving the heat resistance and mechanical characteristics and other properties of these setting type resin compositions, there have been proposed various setting resin type compositions formed by incorporating resol type phenolic resins or novolak type phenolic resins into setting type resins. For example, setting type resin compositions comprising an epoxy resin as the setting type resin and a novolak type phenolic resin incorporated therein are proposed in Japanese Patent Publications Nos. 9246/57, 11827/63, 3574/64, 27769/64, 1352/66, 30351/70, 38030/71, 8278/73, 44958/73, 19319/75, 20537/76, 21679/76, 21839/76, 24399/76, 43403/76, 3828/77, and 9480/77, and Japanese Patent Application Laid-Open Specifications Nos. 72293/73, 118797/74, 118798/74, 70497/75, 108400/75, 132267/76, 138599/77, 144099/77 and 29532/80. Novolak type phenolic resins incorporated in these known epoxy resin compositions are those prepared according to the conventional methods and their number average molecular weights are relatively low, for example, ordinarily lower than 1000 and about 1200 at highest. Even if these novolak type phenolic resins having a relatively low molecular weight are incorporated into epoxy resins, it is impossible to sufficiently improve the heat resistance and mechanical characteristics at high temperatures such as heat distortion temperatures, the heat distortion resistance, flexural strength, mechanical strength and dimensional stability, in the resulting epoxy resin compositions. Furthermore, even if such novolak type phenolic resins having a relatively low molecular weight are incorporated into setting type resins other than epoxy resins, for example, urethane resins, urea resins, melamine resins and phenolic resins, it is impossible to sufficiently improve the heat resistance and mechanical characteristics in the resulting setting type resin compositions.